The membrane glycoproteins specified by herpes simplex virus (HSV) are delivered to two locations within the cell following their synthesis. One is the plasma membrane and the other is the inner nuclear membrane where nucleocapsids acquire their envelopes. Virions initially containing immature glycoproteins are transported out of the cell via the Golgi apparatus. The research proposed here is directed toward answering the following questions: (1) What factors determine that the HSV glycoproteins will be delivered to the inner nuclear membrane? (2) What factors determine that the HSV glycoproteins will be incorporated in virions? Attention will focused on two of the HSV glycoproteins, designated gB and gE, and on G protein of vesicular stomatitis virus. Immunoelectron microscopy will be performed to assess the distribution of these glycoproteins in the membranes of transformed human cells that constitutively express a single viral glycoprotein. The cells will be infected with HSV mutants unable to produce gB or gE, in order to determine whether other HSV products influence the intracellular transport of gB or gE. Mutations will be introduced into the coding regions of gB and gE to define domains required for transport to the inner nuclear membrane, in infected or uninfected cells, and domains required for incorporation into virions. These experiments should yield new information about the intracellular transport and sorting of membrane proteins, addressing problems that have been relatively intractible until now. In addition, the results should contribute to an understanding of processes essential for HSV replication.